2000.03.07 PRB
Citations of the 'to-be-PRB' article (minus the citations already available in proj/fesi).
(Comparison: TODO!!!)
"Important new articles"
Biquadratic coupling
- Origin of Biquadratic Exchange in Fe/Si/Fe
G. J. Strijkers, J. T. Kohlhepp, H. J. M. Swagten, and W. J. M. de Jonge
Physical Review Letters -- February 21, 2000 -- Volume 84, Issue 8, pp. 1812-1815
The thickness and temperature dependences of the interlayer exchange coupling in well-defined molecular beam epitaxy-grown
Fe/Si/Fe sandwich structures have been studied. The biquadratic coupling shows a strong temperature dependence in contrast to the
bilinear coupling. Both depend exponentially on thickness. These observations can be well understood in the framework of
Slonczewski's loose spins model [J. Appl. Phys. 73, 5957 (1993)]. No bilinear contribution of the loose spins to the coupling was
observed. ©2000 The American Physical Society
Articles citing the articles cited in the original paper
-
Field:: Cited author/reference
Statement:: TOSCANO-S-1992-J-MAGN-MAGN-MATER-V114-PL6
SCI CDE with Abstracts (Jan 99 - Dec 99) (D4.1)
- Record 1 of 15.
Title: Magnetic-Properties and Magnetoresistance of Granular Evaporated Fe/Si Films
Authors: Ihara-N Narushima-S Kijima-T Abeta-H Saito-T Shinagawa-K Tsushima-T
Full source: JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 1999, Vol 38, Iss 11, pp 6272-6281
Abstract: Fe (3.4 Angstrom) and Si (6 Angstrom) are evaporated alternately onto silica substrates to realize a granular structure. The substrate temperature T-s during the evaporation is changed from 100 K to 623 K to vary the film structures. The specimens of T-s greater than or equal to room temperature (RT) are superparamagnetic at RT, which suggests a granular structure. Magnetoresistance (MR) at RT is negative (resistivity decreases with increasing magnetic field H) for all specimens. It is thought that the negative MR is attributable to the granular structure. On the other hand, at 77 K a positive MR linear with H (not H-2) up to 50 kOe is observed for all specimens. The linear dependence on H of the positive MR may be due to the nonuniformity in the granular structure. The positive MR itself and the change of the sign of MR from negative to positive with decreasing temperature have not been observed in conventional granular systems such as Co-Ag and Co-Al-O.
Record 2 of 15.
Title: Amorphous Fe-Si and Fe-Ge Nanostructures Quantitatively Analyzed by X-Ray-Photoelectron Spectroscopy
Authors: Schleberger-M Walser-P Hunziker-M Landolt-M
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 20, pp 14360-14365
Abstract: The subject of this paper is an x-ray-photoelectron spectroscopy investigation of amorphous Fe-Si and Fe-Ge nanostructures that have attracted interest because of their magnetic coupling properties. To this end we deposit Fe onto clean, amorphous Si and Ge substrates at room temperature and at 40 K, respectively. We take spectra of the Fe3p, Fe2p, and Si2p core Levels to determine possible chemical shifts. The results indicate a charge transfer from the Fe to the Si and Ge atoms at room temperature as well as at 40 K. Additionally, we record wide range spectra of the SiKLL, GeLMM, and the Fe2p peaks as well as spectra of Fe-Si, and Fe-Ge compounds, respectively. Analyzing the inelastic background of the peaks we quantitatively determine the nanostructure of the deposits. We can exclude the formation of sharp interfaces. Instead, we find evidence for the formation of an Fe-Si or Fe-Ge interface compound with a homogeneous composition. For magnetically investigated low-temperature prepared Fe/Si/Fe trilayers we show that the spacer layer is a pure semiconductor with a thickness that is reduced compared to the nominal value. [S0163-1829(99)02443-1].
Record 3 of 15.
Title: Theory of Interlayer Exchange Interactions in Magnetic Multilayers
Authors: Bruno-P
Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 48, pp 9403-9419
Abstract: This paper presents a review of the phenomenon of interlayer exchange coupling in magnetic multilayers. The emphasis is put on a pedagogical presentation of the mechanism of the phenomenon, which has been successfully explained in terms of a spin-dependent quantum confinement effect. The theoretical predictions are discussed in connection with corresponding experimental investigations.
Record 4 of 15.
Title: Interlayer Exchange Coupling, Crystalline and Magnetic-Structure in Fe/CsCl-Fesi Multilayers Grown by Molecular-Beam Epitaxy
Authors: Dekoster-J Degroote-S Meersschaut-J Moons-R Vantomme-A Bottyan-L Deak-L Szilagyi-E Nagy-DL Baron-AQR Langouche-G
Full source: HYPERFINE INTERACTIONS 1999, Vol 121, Iss 1-4, pp 39-48
Abstract: Crystalline and magnetic structure as well as the interlayer exchange coupling in MBE grown Fe/FeSi multilayers are investigated. From conversion electron Mossbauer spectroscopy and ion beam channeling measurements the spacer FeSi material is found to be stabilized in a crystalline metastable metallic FeSi phase with the CsCl structure. Strong non-oscillatory interlayer exchange coupling is identified with magnetometry and synchrotron Mossbauer reflectometry. From the fits of the time spectrum and the resonant theta-2 theta scans a model for the sublayer magnetization of the multilayer is deduced.
Record 5 of 15.
Title: Magnetic and Electric Properties of Sn-Oxide/M (M=fe, Ni, Co) Multilayers
Authors: Matsuyama-K Nishihata-K Komatsu-S Nozaki-Y
Full source: IEEE TRANSACTIONS ON MAGNETICS 1999, Vol 35, Iss 5, pp 2901-2903
Abstract: Magnetic and electronic properties of novel semiconductive-oxide/ferromagnet multilayers of Sn-oxide and ferromagnetic metals (Fe, Ni, Co), deposited with a multi-target rf magnetron sputtering system, were studied. Among the studied material systems, Co/Sn-oxide sustains well-defined layer structure and ferromagnetic property for the thinnest thickness of 1 nm, A thermionic CPP transport was observed in [Co(2 nm) /Sn-oxide (4 nm)](10), which activation energy was evaluated as 4.4x10(-3) erg from the thermal dependence of conductivity. Negative magnetoresistance was observed in two orthogonal directions of in-plane external fields, which confirms spin dependent transport in Sn-oxide thin film, The measured MR change is 0.6 % (Delta R = 0.8 Omega, R-s=140 Omega) at room temperature.
Record 6 of 15.
Title: Magnetic and Electric Properties of Mn5Ge3/Ge Nanostructured Films
Authors: Miyoshi-T Matsui-T Tsuda-H Mabuchi-H Morii-K
Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 5372-5374
Abstract: We have investigated the magnetic, electric, and structural properties of Mn5Ge3/Ge nanostructured films produced by solid-state reaction of Mn/Ge multilayered films. The films composed of strongly uniaxially oriented Mn5Ge3 and randomly oriented Ge were successfully produced. The average grain size of Mn5Ge3 considerably changed according to the discharging power (E) of the ion source: 15 nm for E = 25 W and 50 nm for E = 50 W. The temperature dependence of the conductivity for the E = 25 sample showed semiconductor-type behavior over all the temperature region. Whereas the E = 50 sample, the conduction type changed from a metallic type (low temperature) to a semiconductor type (high temperature) with the transition temperature T-TR = 360 K. We also observed the anomalous magnetic behavior of Mn5Ge3. We discuss these behaviors in conjunction with the microstructure of the annealed films. The possibility of the carrier-spin exchange interactions has also been studied. (C) 1999 American Institute of Physics. [S0021-8979(99)22208-6].
Record 7 of 15.
Title: Interlayer Coupling of Fe/Si/Fe Trilayers with Very Thin Boundary-Layers
Authors: Endo-Y Kitakami-O Shimada-Y
Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 5741-5743
Abstract: The interlayer magnetic coupling of a Fe/Si/Fe trilayer shows an analogous feature to that of Fe/Si superlattices. With an increase in Si layer thickness, it oscillates as ferromagnetic (first F), antiferromagnetic (AF), ferromagnetic (second F), and finally reaches a noncoupling (N) state. We have investigated interlayer coupling of Fe/Si/Fe trilayers inserting very thin (1 or 2 ML thick) boundary layers X (X=Ag, Ge, Fe-Si, Ta, etc.). They are expected to suppress interatomic diffusion between Fe and Si layers. Interlayer coupling of Fe/X/Si/X/Fe with negligible interdiffusion is simply F and changes to N as the Si layer thickness increases. Furthermore, Fe/Fe-Si/Fe trilayers which show coupling of first F, AF but not second F, reproduce second F when a Si layer is inserted in the Fe-Si spacer. These results imply that an amorphous Si spacer mediates ferromagnetic coupling between neighboring Fe layers while the first F and the strong AF coupling usually observed in Fe/Si superlattices are caused by diffused crystalline Fe-Si. (C) 1999 American Institute of Physics. [S0021-8979(99)45508-2].
Record 8 of 15.
Title: Heat-Induced Effective Exchange Coupling in Magnetic Multilayers with Semiconductors
Authors: Walser-P Hunziker-M Landolt-M
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 95-109
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer layer are exchange coupled across the spacer. The coupling is reversibly temperature dependent with a positive temperature coefficient making such layered systems a 2-D realization of the concept of heat-induced magnetism. By studying ferromagentic Fe layers separated by amorphous Si, Ge, or ZnSe layers we explore the possibilities to generate such an effective exchange coupling and address the question of the mechanism responsible for it. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 9 of 15.
Title: Heat-Induced Coupling in Multilayers with Semiconducting Spacers
Authors: Walser-P Landolt-M
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 412-414
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 10 of 15.
Title: Heat-Induced Antiferromagnetic Coupling in Multilayers with ZnSe Spacers
Authors: Walser-P Hunziker-M Speck-T Landolt-M
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 6, pp 4082-4086
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. As spacer material we use amorphous ZnSe which is a compound semiconductor and find heat-induced antiferromagnetic coupling in striking similarity to amorphous Si and Ge. In an Fe/alpha-ZnSe/Fe trilayer with spacer thickness between 18 Angstrom and 22 Angstrom the coupling is antiferromagnetic with a positive temperature coefficient. At slightly larger thicknesses between 22 Angstrom and 25 Angstrom we find a reversible transition from ferromagnetic coupling at low temperatures to antiferromagnetic coupling at higher temperatures upon heating. We discuss the reversibly heat-induced effective exchange coupling in terms of localized defect states in the band gap in the vicinity of the Fermi energy. [S0163-1829(99)04230-7].
Record 11 of 15.
Title: Cohesive, Structural, and Electronic-Properties of Fe-Si Compounds
Authors: Moroni-EG Wolf-W Hafner-J Podloucky-R
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 20, pp 12860-12871
Abstract: Phase stability, structural, and electronic properties of iron silicides in the Fe3Si, FeSi, and FeSi2 compositions are investigated by first-principle density-functional calculations based on ultrasoft pseudopotentials and all-electron methods. Structural stabilization versus spin-polarization effects are discussed at the Fe3Si composition, while for epsilon-FeSi and beta-FeSi2 we investigate their structural properties and the corresponding semiconducting band properties. All the computed results are analyzed and compared to available experimental data. The stability of the bulk phases, the lattice parameters, the cohesive energies and magnetic properties are found to be in good agreement with experiment when using the generalized gradient approximations for the exchange-correlation functional. Density-functional calculations are unable to account for the small bulk modulus of epsilon-FeSi despite that the computed lattice constant and internal atomic positions coincide with the experimental results. Both full-potential and ultrasoft-pseudopotential methods confirm for beta-FeSi2 the indirect nature of the fundamental gap, which is attributed to a transition between Y to 0.6X Lambda being 30% smaller than the experimental gap. Ultrasoft pseudopotential calculations of Fe-Si magnetic phases and of various nonequilibrium metallic phases at the FeSi and FeSi2 composition are presented. These calculations provide nb initio information concerning the stabilization of metallic pseudomorphic phases via high pressures or epitaxy. [S0163-1829(99)05419-3].
Record 12 of 15.
Title: Interlayer Exchange Coupling Between 2 Ferromagnets with Finite Thickness Separated by a Nonmetallic Spacer
Authors: Wang-JZ Li-BZ
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 9, pp 6383-6389
Abstract: Interlayer exchange coupling (IEC) between two ferromagnets (FM's) separated by a nonmetallic spacer is analyzed theoretically within the free-electron approximation. Particular attention is paid to the influence of FM thickness d(FM) On IEC and the variation of Fermi energy with the alignment of two FM's. The results show that (I)d(FM) strongly influence the IEC such that, only when d(FM) is not large, the barrier height and molecular field are both small, the IEC may oscillate with the spacer thickness owing to the quantum-size effect; otherwise, the IEC does not oscillate, but exhibits an exponential behavior in most spacer thickness; (2) as an oscillatory function of d(FM) with multiple periods, the IEC has a negative nonoscillatory term, which will become zero when the molecular field is comparatively small; (3) the Fermi energy has little difference between the parallel and antiparallel alignments of the two FM's, which correlates with the IEC to some extent. Particularly, with the increasing of d(FM) this correlation becomes stronger. [S0163-1829(99)01409-5].
Record 13 of 15.
Title: Interlayer Coupling in Fe/Fe1-Xsix Superlattices
Authors: Endo-Y Kitakami-O Shimada-Y
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 6, pp 4279-4286
Abstract: Interlayer coupling has been investigated for a series of Fe/Fe1-xSix (0.4 less than or equal to x less than or equal to 1.0) superlattices. The layer of Fe1-xSix in the lattices is ferromagnetic for x<0.5 and causes ferromagnetic coupling between Fe layers for all spacer thicknesses investigated here. As the Si content increases above x=0.5, the layer becomes nonmagnetic and simultaneously our current in the plane of the sample and current perpendicular to the sample plane measurements suggest that the spacer rapidly changes its conduction property from metallic to highly resistive. Variations of the interlayer magnetic coupling as a function of spacer layer thickness for the spacer compositions above x=0.5 are similar to each other; namely, with an increase of the spacer thickness the interlayer coupling is initially ferromagnetic, then antiferromagnetic, and finally becomes noncoupling. Moreover, the temperature dependence of the bilinear and biquadratic coupling constants, J(1)(T) and J(2)(T) which were obtained by numerical fitting, varies sensitively with x. Assuming that the conduction of the spacers ranges from metallic to insulating as x increases, all these coupling behaviors can be described qualitatively by the quantum interference model formalized by Bruno. Furthermore, we found that the coupling strength is enhanced dramatically with increase of x of Fe1-xSix. [S0163-1829(99)11405-X].
Record 14 of 15.
Title: Spin-Polarized Tunnel Current in Magnetic-Layer Systems and Its Relation to the Interlayer Exchange Interaction
Authors: Heide-C Elliott-RJ Wingreen-NS
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 6, pp 4287-4304
Abstract: The spin-polarized tunnel current and its connection to the interlayer exchange interaction is studied in ferromagnet-insulator-ferromagnet thin-film planar junctions out of equilibrium. Building on the nonequilibrium Keldysh formalism, it is possible to systematically include a contact interaction between localized spins and conduction electrons and extend previous treatments on spin currents and exchange interaction. In particular, a Landauer-type formula is derived for the spin current that explains the result found earlier [Schwabe, Wingreen, and Elliott, Phys. Rev. B 54, 12 953 (1996)] that the exchange interaction between the ferromagnetic slabs increases in proportion to the slab width. Furthermore, switching is shown to occur between parallel and antiparallel coupling of the slabs for different applied biases under feasible experimental conditions. [S0163-1829(99)08705-6].
Record 15 of 15.
Title: Antiferromagnetic Coupling in Co/Ge Superlattices
Authors: Endo-Y Kikuchi-N Kitakami-O Shimada-Y
Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 15, pp L133-L137
Abstract: We have investigated interlayer coupling of Co/Ge superlattices. The present experiments obviously show that the coupling changes from ferromagnetic (F) to antiferromagnetic (AF) and finally to non-coupling (N) with the increase of Ge layer thickness. This coupling behaviour, as a function of the spacer thickness, is very similar to that of Fe/Si superlattices, although the coupling strength is much smaller than the latter: namely, similar to 0.05 erg cm(-2) for Co/Ge and similar to 1.0 erg cm(-2) for Fe/Si. Precise structural characterization indicates that diffused spacers at Co/Ge interfaces are responsible for the AF coupling. The same coupling behaviour has also been observed in Co/non-magnetic Co-Ge superlattices, where interdiffusion at the interfaces is entirely suppressed. All these results clearly demonstrate that the interlayer coupling between neighbouring Co layers is mediated by non-magnetic Co-Ge spacers.
SCI CDE with Abstracts (Jan 99 - Dec 99) (D4.1)
Field:: Cited author/reference
Statement:: CHAIKEN-A-1996-PHYS-REV-B-V53-P5518
Record 1 of 18.
Title: Electronic-Structure and Crystalline Coherence in Fe/Si Multilayers
Authors: Carlisle-JA Blankenship-SR Smith-RN Chaiken-A Michel-RP Vanbuuren-T Terminello-LJ Jia-JJ Callcott-TA Ederer-DL
Full source: JOURNAL OF CLUSTER SCIENCE 1999, Vol 10, Iss 4, pp 591-599
Abstract: Soft x-ray fluorescence spectroscopy has been used to examine the electronic structure of deeply buried silicide thin films that arise in Fe/Si multilayers. These systems exhibit antiferromagnetic (AF) coupling of the Fe layers, despite their lack of a noble metal spacer layer found in most GMR materials. Also, the degree of coupling is very dependent on preparation conditions, especially spacer layer thickness and growth temperature. The valence band spectra are quite different for films with different spacerlayer thickness yet are very similar for films grown at different growth temperatures. The latter result is surprising since AF coupling is strongly dependent on growth temperature. Combining near-edge x-ray absorption with the fluorescence data demonstrates that the local bonding structure in the silicide spacer layer in epitaxial films which exhibit AF coupling are metallic. These results indicate the equal roles of crystalline coherence and electronic structure in determining the magnetic properties of these systems.
Record 2 of 18.
Title: Magnetic-Properties and Magnetoresistance of Granular Evaporated Fe/Si Films
Authors: Ihara-N Narushima-S Kijima-T Abeta-H Saito-T Shinagawa-K Tsushima-T
Full source: JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 1999, Vol 38, Iss 11, pp 6272-6281
Abstract: Fe (3.4 Angstrom) and Si (6 Angstrom) are evaporated alternately onto silica substrates to realize a granular structure. The substrate temperature T-s during the evaporation is changed from 100 K to 623 K to vary the film structures. The specimens of T-s greater than or equal to room temperature (RT) are superparamagnetic at RT, which suggests a granular structure. Magnetoresistance (MR) at RT is negative (resistivity decreases with increasing magnetic field H) for all specimens. It is thought that the negative MR is attributable to the granular structure. On the other hand, at 77 K a positive MR linear with H (not H-2) up to 50 kOe is observed for all specimens. The linear dependence on H of the positive MR may be due to the nonuniformity in the granular structure. The positive MR itself and the change of the sign of MR from negative to positive with decreasing temperature have not been observed in conventional granular systems such as Co-Ag and Co-Al-O.
Record 3 of 18.
Title: Amorphous Fe-Si and Fe-Ge Nanostructures Quantitatively Analyzed by X-Ray-Photoelectron Spectroscopy
Authors: Schleberger-M Walser-P Hunziker-M Landolt-M
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 20, pp 14360-14365
Abstract: The subject of this paper is an x-ray-photoelectron spectroscopy investigation of amorphous Fe-Si and Fe-Ge nanostructures that have attracted interest because of their magnetic coupling properties. To this end we deposit Fe onto clean, amorphous Si and Ge substrates at room temperature and at 40 K, respectively. We take spectra of the Fe3p, Fe2p, and Si2p core Levels to determine possible chemical shifts. The results indicate a charge transfer from the Fe to the Si and Ge atoms at room temperature as well as at 40 K. Additionally, we record wide range spectra of the SiKLL, GeLMM, and the Fe2p peaks as well as spectra of Fe-Si, and Fe-Ge compounds, respectively. Analyzing the inelastic background of the peaks we quantitatively determine the nanostructure of the deposits. We can exclude the formation of sharp interfaces. Instead, we find evidence for the formation of an Fe-Si or Fe-Ge interface compound with a homogeneous composition. For magnetically investigated low-temperature prepared Fe/Si/Fe trilayers we show that the spacer layer is a pure semiconductor with a thickness that is reduced compared to the nominal value. [S0163-1829(99)02443-1].
Record 4 of 18.
Title: Interlayer Exchange Coupling, Crystalline and Magnetic-Structure in Fe/CsCl-Fesi Multilayers Grown by Molecular-Beam Epitaxy
Authors: Dekoster-J Degroote-S Meersschaut-J Moons-R Vantomme-A Bottyan-L Deak-L Szilagyi-E Nagy-DL Baron-AQR Langouche-G
Full source: HYPERFINE INTERACTIONS 1999, Vol 121, Iss 1-4, pp 39-48
Abstract: Crystalline and magnetic structure as well as the interlayer exchange coupling in MBE grown Fe/FeSi multilayers are investigated. From conversion electron Mossbauer spectroscopy and ion beam channeling measurements the spacer FeSi material is found to be stabilized in a crystalline metastable metallic FeSi phase with the CsCl structure. Strong non-oscillatory interlayer exchange coupling is identified with magnetometry and synchrotron Mossbauer reflectometry. From the fits of the time spectrum and the resonant theta-2 theta scans a model for the sublayer magnetization of the multilayer is deduced.
Record 5 of 18.
Title: Interlayer Coupling of Fe/Si/Fe Trilayers with Very Thin Boundary-Layers
Authors: Endo-Y Kitakami-O Shimada-Y
Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 5741-5743
Abstract: The interlayer magnetic coupling of a Fe/Si/Fe trilayer shows an analogous feature to that of Fe/Si superlattices. With an increase in Si layer thickness, it oscillates as ferromagnetic (first F), antiferromagnetic (AF), ferromagnetic (second F), and finally reaches a noncoupling (N) state. We have investigated interlayer coupling of Fe/Si/Fe trilayers inserting very thin (1 or 2 ML thick) boundary layers X (X=Ag, Ge, Fe-Si, Ta, etc.). They are expected to suppress interatomic diffusion between Fe and Si layers. Interlayer coupling of Fe/X/Si/X/Fe with negligible interdiffusion is simply F and changes to N as the Si layer thickness increases. Furthermore, Fe/Fe-Si/Fe trilayers which show coupling of first F, AF but not second F, reproduce second F when a Si layer is inserted in the Fe-Si spacer. These results imply that an amorphous Si spacer mediates ferromagnetic coupling between neighboring Fe layers while the first F and the strong AF coupling usually observed in Fe/Si superlattices are caused by diffused crystalline Fe-Si. (C) 1999 American Institute of Physics. [S0021-8979(99)45508-2].
Record 6 of 18.
Title: Heat-Induced Effective Exchange Coupling in Magnetic Multilayers with Semiconductors
Authors: Walser-P Hunziker-M Landolt-M
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 95-109
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer layer are exchange coupled across the spacer. The coupling is reversibly temperature dependent with a positive temperature coefficient making such layered systems a 2-D realization of the concept of heat-induced magnetism. By studying ferromagentic Fe layers separated by amorphous Si, Ge, or ZnSe layers we explore the possibilities to generate such an effective exchange coupling and address the question of the mechanism responsible for it. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 7 of 18.
Title: Transport-Properties of Sputtered Fe Si Multilayers
Authors: Tong-LN Pan-MH Wu-XS Lu-M Zhai-HR
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 101-103
Abstract: A relatively large GMR effect associated with antiferromagnetic (AFM) coupling in sputtered Fe/Si multilayers was observed and the dependence of transport properties on Si layer and Fe layer thickness and on the number of bilayers at room temperature and 77 K were studied. Our data suggests that the mechanism of AFM coupling and GMR effect in Fe/Si multilayers is the same as that in metal/metal systems. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 8 of 18.
Title: Heat-Induced Coupling in Multilayers with Semiconducting Spacers
Authors: Walser-P Landolt-M
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 412-414
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 9 of 18.
Title: Low-Temperature Enhancement of the Magnetic-Anisotropy in Fe Si Multilayers
Authors: Zuberek-R Fronc-K Szymczak-R Baran-M Mosiniewiczszablewska-E Gnatchenkob-SL Chizhik-AB Stobiecki-F Szymczak-H
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 197, Iss MAY, pp 83-84
Abstract: The FMR and SQUID investigation of the magnetic anisotropy of Fe/Si multilayers are presented. The multilayers, with various thicknesses of iron and a thick layer of silicon (in order to eliminate the coupling between Fe layers), have been grown by DC sputtering on single crystal GaAs substrates. Low temperature enhancement of the easy-plane anisotropy, especially below 50 K, was observed. This anisotropy seems to be of magnetoelastic origin. The coercivity was shown to decrease with temperature. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 10 of 18.
Title: Investigation of Interfacial Phenomena in Ag-Si Multilayers During the Annealing Process
Authors: Zhao-JH Zhang-M Liu-RP Zhang-XY Cao-LM Dai-DY Chen-H Xu-YF Wang-WK
Full source: JOURNAL OF MATERIALS RESEARCH 1999, Vol 14, Iss 7, pp 2888-2892
Abstract: Interfacial phenomena and microstructure in Ag-Si multilayers with a modulation period of 7.64 nm during annealing from 323 to 573 K were investigated by in situ x-ray diffraction and high-resolution transmission electron microscopy. Uphill and downhill diffusion were observed on annealing. The temperature dependence of the effective diffusion coefficient from 373 K (as to downhill diffusion regime) to 523 K was D-e = 2.02 x 10(-20) exp(-0.24 eV/k(B)T) m(2)/s. Diffusion of silicon atoms along silver grain boundaries was proposed as the main diffusion mechanism. After annealing, continuous silver sublayers changed to nanometer-sized silver particles (about 4.5 nm) coated completely by amorphous silicon.
Record 11 of 18.
Title: Design and Performance of an Ultrahigh-Vacuum System for Metallic Multilayers
Authors: Chaudhari-SM Suresh-N Phase-DM Gupta-A Dasannacharya-BA
Full source: JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS 1999, Vol 17, Iss 1, pp 242-248
Abstract: This article describes the design, development, and performance testing of a versatile ultrahigh vacuum (UHV) electron-beam deposition system for synthesis of thin films and multilayer structures. Initially, basic design norms required to achieve set objectives are discussed and then a brief description of the system is presented. The fabricated UHV chamber has a number of vacuum ports to accommodate various features and accessories needed to deposit and characterize good quality thin films and multilayer structures of different metals. To demonstrate the capabilities of the system, depositions of thin films and multilayer structures of different materials were carried out. Representative results of hard x-ray reflectivity measurements corresponding to Ni, Au, and Ag thin films and Nb/Si and Fe/Ni multilayer structures are given and discussed. Furthermore, the easy adaptability of the system in order to carry out other investigations related to thin films is also demonstrated by presenting our recent in situ experiments conducted on aging studies of discontinuous silver films deposited on glass substrates under UHV conditions. (C) 1999 American Vacuum Society. [S0734-2101(99)01001-5].
Record 12 of 18.
Title: Epitaxial-Growth of Fe(001) on CoSi2(001)/Si(001) Surfaces - Structural and Electronic-Properties
Authors: Bertoncini-P Wetzel-P Berling-D Gewinner-G Ulhaqbouillet-C Bohnes-VP
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 15, pp 11123-11130
Abstract: Ultrathin Fe films, in the thickness range 0-40 monolayers (ML), have been grown on Si(001) by molecular-beam epitaxy and characterized by low-energy electron diffraction, inelastic medium-energy electron diffraction, x-ray photoelectron spectroscopy, angular-resolved ultraviolet spectroscopy, x-ray photoelectron diffraction, ion scattering spectroscopy, and transmission electron microscopy. For Fe depositions onto Si(001) at room temperature, a disordered layer is obtained due to a high degree of intermixing between the Fe deposit and the Si substrate. Successful epitaxial growth of Fe at room temperature is achieved by use of a thin (similar to 10 Angstrom) CoSi2 silicide interlayer epitaxially grown on the Si(001) substrate prior to the Fe deposition, which prevents the intermixing of the Si substrate atoms into the Fe overlayer. Below a coverage of similar to 2 ML a reacted ordered iron-rich phase forms at the surface. At higher coverages, there is growth of an epitaxial essentially body-centered cubic (bcc) Fe(001) overlayer with the orientational relationships Fe(001)[001]parallel to CoSi2(001)[001]parallel to Si(001)[001]. Finally, a well-ordered Fe/CoSi2 interface is formed even at room temperature. [S0163-1829(99)12335-X].
Record 13 of 18.
Title: Formation of Nonmagnetic C-Fe1-Xsi in Antiferromagnetically Coupled Epitaxial Fe/Si/Fe
Authors: Strijkers-GJ Kohlhepp-JT Swagten-HJM Dejonge-WJM
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 13, pp 9583-9587
Abstract: Low-energy electron diffraction, Auger electron spectroscopy, and conversion electron Mossbauer spectroscopy have been applied to study antiferromagnetically exchange-coupled epitaxial Fe/Si/Fe(100). It is shown that a bcc-like (100) structure is maintained throughout the layers after a recrystallization of the spacer layer by Fe/Si interdiffusion. Direct experimental evidence is presented that c-Fe1-xSi (0 less than or equal to x less than or equal to 0.5) is formed in the spacer layer, a nonmagnetic metallic metastable iron silicide phase with a CsCl structure (B2), which supports explanations for the antiferromagnetic exchange coupling given recently.
Record 14 of 18.
Title: Heat-Induced Antiferromagnetic Coupling in Multilayers with ZnSe Spacers
Authors: Walser-P Hunziker-M Speck-T Landolt-M
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 6, pp 4082-4086
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. As spacer material we use amorphous ZnSe which is a compound semiconductor and find heat-induced antiferromagnetic coupling in striking similarity to amorphous Si and Ge. In an Fe/alpha-ZnSe/Fe trilayer with spacer thickness between 18 Angstrom and 22 Angstrom the coupling is antiferromagnetic with a positive temperature coefficient. At slightly larger thicknesses between 22 Angstrom and 25 Angstrom we find a reversible transition from ferromagnetic coupling at low temperatures to antiferromagnetic coupling at higher temperatures upon heating. We discuss the reversibly heat-induced effective exchange coupling in terms of localized defect states in the band gap in the vicinity of the Fermi energy. [S0163-1829(99)04230-7].
Record 15 of 18.
Title: Interlayer Coupling in Fe/Fe1-Xsix Superlattices
Authors: Endo-Y Kitakami-O Shimada-Y
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 6, pp 4279-4286
Abstract: Interlayer coupling has been investigated for a series of Fe/Fe1-xSix (0.4 less than or equal to x less than or equal to 1.0) superlattices. The layer of Fe1-xSix in the lattices is ferromagnetic for x<0.5 and causes ferromagnetic coupling between Fe layers for all spacer thicknesses investigated here. As the Si content increases above x=0.5, the layer becomes nonmagnetic and simultaneously our current in the plane of the sample and current perpendicular to the sample plane measurements suggest that the spacer rapidly changes its conduction property from metallic to highly resistive. Variations of the interlayer magnetic coupling as a function of spacer layer thickness for the spacer compositions above x=0.5 are similar to each other; namely, with an increase of the spacer thickness the interlayer coupling is initially ferromagnetic, then antiferromagnetic, and finally becomes noncoupling. Moreover, the temperature dependence of the bilinear and biquadratic coupling constants, J(1)(T) and J(2)(T) which were obtained by numerical fitting, varies sensitively with x. Assuming that the conduction of the spacers ranges from metallic to insulating as x increases, all these coupling behaviors can be described qualitatively by the quantum interference model formalized by Bruno. Furthermore, we found that the coupling strength is enhanced dramatically with increase of x of Fe1-xSix. [S0163-1829(99)11405-X].
Record 16 of 18.
Title: Microscopic Environment of Fe in Epitaxially Stabilized C-Fesi
Authors: Fanciulli-M Weyer-G Svane-A Christensen-NE Vonkanel-H Muller-E Onda-N Miglio-L Tavazza-F Celino-M
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 5, pp 3675-3687
Abstract: Epitaxially stabilized iron monosilicide films having the CsCl structure (c-FeSi) have been investigated by conversion electron Mossbauer spectroscopy and transmission electron microscopy. The Fe-57 Mossbauer parameters (isomer shift delta, linewidth Gamma, and quadrupole splitting Delta) are reported and discussed in terms of the local surrounding of the Fe nucleus. High statistical accuracy and resolution allowed a detailed investigation of the effects of strain and of the structural phase transformation from the epitaxially stabilized to the bulk stable phase, The phase transformation was found to proceed in a rather surprising layer by layer mechanism with smooth interfaces between the epitaxially stabilized, the bulk stable, and a third phase. Results from a molecular-dynamics simulation at constant pressure and temperature of the structural phase transition are presented and compared with the experimental findings. The isomer shift and the electric-field gradient at the Fe nucleus in the strained c-FeSi and in the third phase have been calculated using the ab initio full potential linear muffin-tin orbital method. The Mossbauer parameters of some relevant point defects in c-FeSi have likewise been calculated within this framework. [S0163-1829(99)01302-8].
Record 17 of 18.
Title: Antiferromagnetic Coupling in Co/Ge Superlattices
Authors: Endo-Y Kikuchi-N Kitakami-O Shimada-Y
Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 15, pp L133-L137
Abstract: We have investigated interlayer coupling of Co/Ge superlattices. The present experiments obviously show that the coupling changes from ferromagnetic (F) to antiferromagnetic (AF) and finally to non-coupling (N) with the increase of Ge layer thickness. This coupling behaviour, as a function of the spacer thickness, is very similar to that of Fe/Si superlattices, although the coupling strength is much smaller than the latter: namely, similar to 0.05 erg cm(-2) for Co/Ge and similar to 1.0 erg cm(-2) for Fe/Si. Precise structural characterization indicates that diffused spacers at Co/Ge interfaces are responsible for the AF coupling. The same coupling behaviour has also been observed in Co/non-magnetic Co-Ge superlattices, where interdiffusion at the interfaces is entirely suppressed. All these results clearly demonstrate that the interlayer coupling between neighbouring Co layers is mediated by non-magnetic Co-Ge spacers.
Record 18 of 18.
Title: Magnetic Superlattices and Multilayers
Authors: Schuller-IK Kim-S Leighton-C
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 571-582
Abstract: We briefly review the active areas of current research in magnetic superlattices, emphasizing later years. With recent widening use of advanced technologies, more emphasis has been made on quantitative atomic level chemical and structural characterization. Examples where the multilayer structure has been controlled, characterized and correlated with the physical properties are discussed. The physical properties are categorized according to the complexity of a structure needed to observe a particular effect. We outline a number of general important unsolved problems, which could considerably benefit from theoretical and experimental input. An extensive list of magnetic multilayer materials is provided, with references to recent publications. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
SCI CDE with Abstract:s (Jan 99 - Dec 99) (D4.1)
Field:: Cited author/reference
Statement:: MATTSON-JE-1993-PHYS-REV-LETT-V71-P185
Record 1 of 11.
Title: Electronic-Structure and Crystalline Coherence in Fe/Si Multilayers
Authors: Carlisle-JA Blankenship-SR Smith-RN Chaiken-A Michel-RP Vanbuuren-T Terminello-LJ Jia-JJ Callcott-TA Ederer-DL
Full source: JOURNAL OF CLUSTER SCIENCE 1999, Vol 10, Iss 4, pp 591-599
Abstract: Soft x-ray fluorescence spectroscopy has been used to examine the electronic structure of deeply buried silicide thin films that arise in Fe/Si multilayers. These systems exhibit antiferromagnetic (AF) coupling of the Fe layers, despite their lack of a noble metal spacer layer found in most GMR materials. Also, the degree of coupling is very dependent on preparation conditions, especially spacer layer thickness and growth temperature. The valence band spectra are quite different for films with different spacerlayer thickness yet are very similar for films grown at different growth temperatures. The latter result is surprising since AF coupling is strongly dependent on growth temperature. Combining near-edge x-ray absorption with the fluorescence data demonstrates that the local bonding structure in the silicide spacer layer in epitaxial films which exhibit AF coupling are metallic. These results indicate the equal roles of crystalline coherence and electronic structure in determining the magnetic properties of these systems.
Record 2 of 11.
Title: Magnetic-Properties and Magnetoresistance of Granular Evaporated Fe/Si Films
Authors: Ihara-N Narushima-S Kijima-T Abeta-H Saito-T Shinagawa-K Tsushima-T
Full source: JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 1999, Vol 38, Iss 11, pp 6272-6281
Abstract: Fe (3.4 Angstrom) and Si (6 Angstrom) are evaporated alternately onto silica substrates to realize a granular structure. The substrate temperature T-s during the evaporation is changed from 100 K to 623 K to vary the film structures. The specimens of T-s greater than or equal to room temperature (RT) are superparamagnetic at RT, which suggests a granular structure. Magnetoresistance (MR) at RT is negative (resistivity decreases with increasing magnetic field H) for all specimens. It is thought that the negative MR is attributable to the granular structure. On the other hand, at 77 K a positive MR linear with H (not H-2) up to 50 kOe is observed for all specimens. The linear dependence on H of the positive MR may be due to the nonuniformity in the granular structure. The positive MR itself and the change of the sign of MR from negative to positive with decreasing temperature have not been observed in conventional granular systems such as Co-Ag and Co-Al-O.
Record 3 of 11.
Title: Theory of Interlayer Exchange Interactions in Magnetic Multilayers
Authors: Bruno-P
Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 48, pp 9403-9419
Abstract: This paper presents a review of the phenomenon of interlayer exchange coupling in magnetic multilayers. The emphasis is put on a pedagogical presentation of the mechanism of the phenomenon, which has been successfully explained in terms of a spin-dependent quantum confinement effect. The theoretical predictions are discussed in connection with corresponding experimental investigations.
Record 4 of 11.
Title: Epitaxial Mnas/GaAs/Mnas Trilayer Magnetic Heterostructures
Authors: Tanaka-M Saito-K Nishinaga-T
Full source: APPLIED PHYSICS LETTERS 1999, Vol 74, Iss 1, pp 64-66
Abstract: We have successfully grown MnAs/GaAs/MnAs ferromagnet/semiconductor trilayer heterostructures on GaAs(111) B substrates by molecular beam epitaxy. The epitaxial orientations of MnAs and GaAs are (0001) and (111), respectively, as expected. It was found that epitaxial monocrystalline GaAs can be grown on the As-rich (3X2)-(0001) MnAs surface. Cross-sectional images by transmission electron microscopy showed that the trilayers are formed as intended with fairly smooth and atomically abrupt interfaces. Double-step features were observed in magnetization characteristics due to the difference in coercive force between the top and bottom MnAs layers. The interlayer coupling was small when the thickness of the GaAs spacer layer was 5-10 nm. (C) 1999 American Institute of Physics. [S0003-6951(99)02101-4].
Record 5 of 11.
Title: Interlayer Exchange Coupling, Crystalline and Magnetic-Structure in Fe/CsCl-Fesi Multilayers Grown by Molecular-Beam Epitaxy
Authors: Dekoster-J Degroote-S Meersschaut-J Moons-R Vantomme-A Bottyan-L Deak-L Szilagyi-E Nagy-DL Baron-AQR Langouche-G
Full source: HYPERFINE INTERACTIONS 1999, Vol 121, Iss 1-4, pp 39-48
Abstract: Crystalline and magnetic structure as well as the interlayer exchange coupling in MBE grown Fe/FeSi multilayers are investigated. From conversion electron Mossbauer spectroscopy and ion beam channeling measurements the spacer FeSi material is found to be stabilized in a crystalline metastable metallic FeSi phase with the CsCl structure. Strong non-oscillatory interlayer exchange coupling is identified with magnetometry and synchrotron Mossbauer reflectometry. From the fits of the time spectrum and the resonant theta-2 theta scans a model for the sublayer magnetization of the multilayer is deduced.
Record 6 of 11.
Title: Ferromagnet Semiconductor Hybrid Structures Grown by Molecular-Beam Epitaxy
Authors: Tanaka-M
Full source: JOURNAL OF CRYSTAL GROWTH 1999, Vol 202, Iss MAY, pp 660-669
Abstract: Recent studies on two types of ferromagnet/semiconductor hybrid structures grown by molecular-beam epitaxy (MBE) are described: (1) ferromagnet [MnAs]/semiconductor [GaAs] layered heterostructures, and (2) III-V (GaAs)-based magnetic semiconductor alloy [(GaMn)As] thin films. Their MBE growth, structures, and magnetic properties are presented. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 7 of 11.
Title: Transport-Properties of Sputtered Fe Si Multilayers
Authors: Tong-LN Pan-MH Wu-XS Lu-M Zhai-HR
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 101-103
Abstract: A relatively large GMR effect associated with antiferromagnetic (AFM) coupling in sputtered Fe/Si multilayers was observed and the dependence of transport properties on Si layer and Fe layer thickness and on the number of bilayers at room temperature and 77 K were studied. Our data suggests that the mechanism of AFM coupling and GMR effect in Fe/Si multilayers is the same as that in metal/metal systems. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 8 of 11.
Title: Epitaxial-Growth and Properties of Mnas/GaAs/Mnas Trilayer Heterostructures
Authors: Tanaka-M Saito-K Goto-M Nishinaga-T
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 719-721
Abstract: We have grown MnAs/GaAs/MnAs ferromagnet/semiconductor trilayer heterostructures on GaAs (1 1 1)B substrates by molecular-beam epitaxy. Cross-sectional transmission electron microscopy showed that the trilayers are formed as intended with fairly abrupt and smooth interfaces. The epitaxial orientations of MnAs and GaAs are (0 0 0 1) and (1 1 1), respectively. Double steps were observed in the magnetization characteristics due to the difference in coercive force between the two MnAs layers. The interlayer coupling was little when the thickness of the GaAs was 5-10 nm. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 9 of 11.
Title: Cohesive, Structural, and Electronic-Properties of Fe-Si Compounds
Authors: Moroni-EG Wolf-W Hafner-J Podloucky-R
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 20, pp 12860-12871
Abstract: Phase stability, structural, and electronic properties of iron silicides in the Fe3Si, FeSi, and FeSi2 compositions are investigated by first-principle density-functional calculations based on ultrasoft pseudopotentials and all-electron methods. Structural stabilization versus spin-polarization effects are discussed at the Fe3Si composition, while for epsilon-FeSi and beta-FeSi2 we investigate their structural properties and the corresponding semiconducting band properties. All the computed results are analyzed and compared to available experimental data. The stability of the bulk phases, the lattice parameters, the cohesive energies and magnetic properties are found to be in good agreement with experiment when using the generalized gradient approximations for the exchange-correlation functional. Density-functional calculations are unable to account for the small bulk modulus of epsilon-FeSi despite that the computed lattice constant and internal atomic positions coincide with the experimental results. Both full-potential and ultrasoft-pseudopotential methods confirm for beta-FeSi2 the indirect nature of the fundamental gap, which is attributed to a transition between Y to 0.6X Lambda being 30% smaller than the experimental gap. Ultrasoft pseudopotential calculations of Fe-Si magnetic phases and of various nonequilibrium metallic phases at the FeSi and FeSi2 composition are presented. These calculations provide nb initio information concerning the stabilization of metallic pseudomorphic phases via high pressures or epitaxy. [S0163-1829(99)05419-3].
Record 10 of 11.
Title: Interlayer Exchange Coupling Between 2 Ferromagnets with Finite Thickness Separated by a Nonmetallic Spacer
Authors: Wang-JZ Li-BZ
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 9, pp 6383-6389
Abstract: Interlayer exchange coupling (IEC) between two ferromagnets (FM's) separated by a nonmetallic spacer is analyzed theoretically within the free-electron approximation. Particular attention is paid to the influence of FM thickness d(FM) On IEC and the variation of Fermi energy with the alignment of two FM's. The results show that (I)d(FM) strongly influence the IEC such that, only when d(FM) is not large, the barrier height and molecular field are both small, the IEC may oscillate with the spacer thickness owing to the quantum-size effect; otherwise, the IEC does not oscillate, but exhibits an exponential behavior in most spacer thickness; (2) as an oscillatory function of d(FM) with multiple periods, the IEC has a negative nonoscillatory term, which will become zero when the molecular field is comparatively small; (3) the Fermi energy has little difference between the parallel and antiparallel alignments of the two FM's, which correlates with the IEC to some extent. Particularly, with the increasing of d(FM) this correlation becomes stronger. [S0163-1829(99)01409-5].
Record 11 of 11.
Title: Magnetotransport Properties of All Semiconductor (Ga,Mn)as/(Al,Ga)as/(Ga,Mn)as Tri-Layer Structures
Authors: Matsukura-F Akiba-N Shen-A Ohno-Y Oiwa-A Katsumoto-S Iye-Y Ohno-H
Full source: PHYSICA B 1998, Vol 258, Iss DEC, pp 573-576
Abstract: To investigate the magnetic coupling in all-semiconductor structure, ferromagnet/nonmagnet/ferromagnet tri-layer structures using (Ga,Mn)As as a ferromagnetic layer and GaAs or (Al,Ga)As as a nonmagnetic layer were prepared and their magnetic and magnetotransport properties were investigated. The results show that the interaction between the two (Ga,Mn)As layers decreases as the GaAs thickness increases or Al content of the (Al,Ga)As spacer increases. This shows that the carriers present in the nonmagnetic layer mediate the magnetic coupling between the two ferromagnetic layers in the present all-semiconductor system. (C) 1998 Elsevier Science B.V. All rights reserved.
SCI CDE with Abstract:s (Jan 99 - Dec 99) (D4.1)
Field:: Cited author/reference
Statement:: FULLERTON-EE-1996-PHYS-REV-B-V53-P5112
Record 1 of 7.
Title: Electronic-Structure and Crystalline Coherence in Fe/Si Multilayers
Authors: Carlisle-JA Blankenship-SR Smith-RN Chaiken-A Michel-RP Vanbuuren-T Terminello-LJ Jia-JJ Callcott-TA Ederer-DL
Full source: JOURNAL OF CLUSTER SCIENCE 1999, Vol 10, Iss 4, pp 591-599
Abstract: Soft x-ray fluorescence spectroscopy has been used to examine the electronic structure of deeply buried silicide thin films that arise in Fe/Si multilayers. These systems exhibit antiferromagnetic (AF) coupling of the Fe layers, despite their lack of a noble metal spacer layer found in most GMR materials. Also, the degree of coupling is very dependent on preparation conditions, especially spacer layer thickness and growth temperature. The valence band spectra are quite different for films with different spacerlayer thickness yet are very similar for films grown at different growth temperatures. The latter result is surprising since AF coupling is strongly dependent on growth temperature. Combining near-edge x-ray absorption with the fluorescence data demonstrates that the local bonding structure in the silicide spacer layer in epitaxial films which exhibit AF coupling are metallic. These results indicate the equal roles of crystalline coherence and electronic structure in determining the magnetic properties of these systems.
Record 2 of 7.
Title: Interlayer Coupling of Fe/Si/Fe Trilayers with Very Thin Boundary-Layers
Authors: Endo-Y Kitakami-O Shimada-Y
Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 5741-5743
Abstract: The interlayer magnetic coupling of a Fe/Si/Fe trilayer shows an analogous feature to that of Fe/Si superlattices. With an increase in Si layer thickness, it oscillates as ferromagnetic (first F), antiferromagnetic (AF), ferromagnetic (second F), and finally reaches a noncoupling (N) state. We have investigated interlayer coupling of Fe/Si/Fe trilayers inserting very thin (1 or 2 ML thick) boundary layers X (X=Ag, Ge, Fe-Si, Ta, etc.). They are expected to suppress interatomic diffusion between Fe and Si layers. Interlayer coupling of Fe/X/Si/X/Fe with negligible interdiffusion is simply F and changes to N as the Si layer thickness increases. Furthermore, Fe/Fe-Si/Fe trilayers which show coupling of first F, AF but not second F, reproduce second F when a Si layer is inserted in the Fe-Si spacer. These results imply that an amorphous Si spacer mediates ferromagnetic coupling between neighboring Fe layers while the first F and the strong AF coupling usually observed in Fe/Si superlattices are caused by diffused crystalline Fe-Si. (C) 1999 American Institute of Physics. [S0021-8979(99)45508-2].
Record 3 of 7.
Title: Heat-Induced Effective Exchange Coupling in Magnetic Multilayers with Semiconductors
Authors: Walser-P Hunziker-M Landolt-M
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 95-109
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer layer are exchange coupled across the spacer. The coupling is reversibly temperature dependent with a positive temperature coefficient making such layered systems a 2-D realization of the concept of heat-induced magnetism. By studying ferromagentic Fe layers separated by amorphous Si, Ge, or ZnSe layers we explore the possibilities to generate such an effective exchange coupling and address the question of the mechanism responsible for it. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 4 of 7.
Title: Heat-Induced Coupling in Multilayers with Semiconducting Spacers
Authors: Walser-P Landolt-M
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 412-414
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 5 of 7.
Title: Heat-Induced Antiferromagnetic Coupling in Multilayers with ZnSe Spacers
Authors: Walser-P Hunziker-M Speck-T Landolt-M
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 6, pp 4082-4086
Abstract: Two ferromagnetic films separated by an amorphous semiconducting spacer are exchange coupled across the spacer layer. The coupling is reversibly temperature dependent with a positive temperature coefficient. As spacer material we use amorphous ZnSe which is a compound semiconductor and find heat-induced antiferromagnetic coupling in striking similarity to amorphous Si and Ge. In an Fe/alpha-ZnSe/Fe trilayer with spacer thickness between 18 Angstrom and 22 Angstrom the coupling is antiferromagnetic with a positive temperature coefficient. At slightly larger thicknesses between 22 Angstrom and 25 Angstrom we find a reversible transition from ferromagnetic coupling at low temperatures to antiferromagnetic coupling at higher temperatures upon heating. We discuss the reversibly heat-induced effective exchange coupling in terms of localized defect states in the band gap in the vicinity of the Fermi energy. [S0163-1829(99)04230-7].
Record 6 of 7.
Title: Interlayer Coupling in Fe/Fe1-Xsix Superlattices
Authors: Endo-Y Kitakami-O Shimada-Y
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 6, pp 4279-4286
Abstract: Interlayer coupling has been investigated for a series of Fe/Fe1-xSix (0.4 less than or equal to x less than or equal to 1.0) superlattices. The layer of Fe1-xSix in the lattices is ferromagnetic for x<0.5 and causes ferromagnetic coupling between Fe layers for all spacer thicknesses investigated here. As the Si content increases above x=0.5, the layer becomes nonmagnetic and simultaneously our current in the plane of the sample and current perpendicular to the sample plane measurements suggest that the spacer rapidly changes its conduction property from metallic to highly resistive. Variations of the interlayer magnetic coupling as a function of spacer layer thickness for the spacer compositions above x=0.5 are similar to each other; namely, with an increase of the spacer thickness the interlayer coupling is initially ferromagnetic, then antiferromagnetic, and finally becomes noncoupling. Moreover, the temperature dependence of the bilinear and biquadratic coupling constants, J(1)(T) and J(2)(T) which were obtained by numerical fitting, varies sensitively with x. Assuming that the conduction of the spacers ranges from metallic to insulating as x increases, all these coupling behaviors can be described qualitatively by the quantum interference model formalized by Bruno. Furthermore, we found that the coupling strength is enhanced dramatically with increase of x of Fe1-xSix. [S0163-1829(99)11405-X].
Record 7 of 7.
Title: Antiferromagnetic Coupling in Co/Ge Superlattices
Authors: Endo-Y Kikuchi-N Kitakami-O Shimada-Y
Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 15, pp L133-L137
Abstract: We have investigated interlayer coupling of Co/Ge superlattices. The present experiments obviously show that the coupling changes from ferromagnetic (F) to antiferromagnetic (AF) and finally to non-coupling (N) with the increase of Ge layer thickness. This coupling behaviour, as a function of the spacer thickness, is very similar to that of Fe/Si superlattices, although the coupling strength is much smaller than the latter: namely, similar to 0.05 erg cm(-2) for Co/Ge and similar to 1.0 erg cm(-2) for Fe/Si. Precise structural characterization indicates that diffused spacers at Co/Ge interfaces are responsible for the AF coupling. The same coupling behaviour has also been observed in Co/non-magnetic Co-Ge superlattices, where interdiffusion at the interfaces is entirely suppressed. All these results clearly demonstrate that the interlayer coupling between neighbouring Co layers is mediated by non-magnetic Co-Ge spacers.
SCI CDE with Abstract:s (Jan 99 - Dec 99) (D4.1)
Field:: Cited author/reference
Statement:: SLONCZEWSKI-JC-1995-J-MAGN-MAGN-MATER-V150-P13
Record 1 of 27.
Title: Proximity Effect in Exchange-Coupled Fe/Cr(001) Superlattices
Authors: Schmitte-T Schreyer-A Leiner-V Siebrecht-R Theisbrohl-K Zabel-H
Full source: EUROPHYSICS LETTERS 1999, Vol 48, Iss 6, pp 692-698
Abstract: Using temperature-dependent measurements of the magneto-optical Kerr effect. (MOKE) we map out a magnetic phase diagram of Fe/Cr(001) superlattices with Cr-thicknesses between 10 to 45 Angstrom in a temperature range from 10 to 700 K. By comparison with neutron scattering results, we demonstrate the strong correlation between different magnetic phases of the Cr interlayers and the coupling between the Fe lavers. Mie find an enhancement of the Cr Neel temperature as we reduce the Cr thicknesses, indicating a strong proximity effect between the Fe and Cr layers.
Record 2 of 27.
Title: Inhomogeneous Ferromagnetic-Resonance Modes in (Fe/Cr)(N) Superlattices with a High Biquadratic Exchange Constant
Authors: Drovosekov-AB Zhotikova-OV Kreines-NM Kholin-DI Meshcheryakov-VF Milyaev-MA Romashev-LN Ustinov-VV
Full source: JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS 1999, Vol 89, Iss 5, pp 986-994
Abstract: In a set of [Fe/Cr](n) superlattices, magnetization curves and spectra of ferromagnetic resonance under an in-plane magnetic field have been studied at room temperature. Along with the acoustic branch, several additional branches have been observed in resonance spectra. Resonance spectra have been calculated analytically for a structure with an infinite number of layers and numerically for finite numbers of layers in real samples using a model of biquadratic exchange taking account of the fourth-order magnetic anisotropy. A possibility of describing both static and resonance properties of the system in terms of this model has been demonstrated. (C) 1999 American Institute of Physics. [S1063-7761(99)02311-2].
Record 3 of 27.
Title: Exchange Coupling in Co-Ti Layered Structures
Authors: Smardz-L
Full source: SOLID STATE COMMUNICATIONS 1999, Vol 112, Iss 12, pp 693-698
Abstract: The Co-Ti multilayers with constant thickness sublayers and Co-d(Ti)-Ti-Co trilayers with wedge-shaped Ti interlayers were prepared using an ultra high vacuum (5 x 10(-10) mbar) DC-RF magnetron sputtering. The planar growth of the Co and Ti sublayers was confirmed in situ by X-ray photoelectron spectroscopy. The Co sublayers grow in the soft magnetic nanocrystalline phase (with average grain size D << 10 nn) up to a critical thickness d(crit) similar to 3 nm. For a thickness greater than d(crit), the Co sublayers undergo a structural transition to the polycrystalline phase with D > 10 nm. Results show that the Co sublayers are very weakly exchange coupled or decoupled for d(Ti) > 2.7 nn. The rapid decrease of the interlayer exchange coupling could be explained by its strong damping due to the formation of a non-magnetic quasi-amorphous Co-Ti alloy layer at the interfaces. The nanocrystalline Co sublayers with d(Co) = 2.2 nm showed a weak 90 degrees coupling near the transition zone (d(Ti) similar to 2 nm) from ferromagnetic to week antiferromagnetic coupling. (C) 1999 Elsevier Science Ltd. All rights reserved.
Record 4 of 27.
Title: Magnetism of Chromium at Surfaces, at Interfaces and in Thin-Films
Authors: Zabel-H
Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 48, pp 9303-9346
Abstract: The spin density wave (SDW) magnetism of thin epitaxial Cr films has recently become the focus of interest because of its mediating role in exchange coupled superlattices. While the incommensurate SDW magnetism and the Neel temperature are well established for bulk Cr, the question arises of how these properties are altered in thin films and superlattices either due to dimensionality effects or due to proximity with the ferromagnetic or paramagnetic boundary layers. After a brief introduction to the basic properties of bulk Cr, this review provides an overview of the SDW magnetism in thin Cr films, starting with surface properties and continuing with the discussion of Cr films of various thickness. The emphasis is more on SDW order in different confined environments than on exchange coupling. The scaling of the Neel temperature with thickness, the critical thickness for the onset of SDW order, the orientation of the SDW wave vector in different environments and the enhancement of SDW order due to proximity effects are extensively discussed. Most important is the role of the interface roughness in case of contact with a ferromagnetic layer. Conflicting results obtained with different experimental techniques are critically reviewed and an interpretation of the SDW order depending on interface quality is proposed.
Record 5 of 27.
Title: Theory of Interlayer Exchange Interactions in Magnetic Multilayers
Authors: Bruno-P
Full source: JOURNAL OF PHYSICS-CONDENSED MATTER 1999, Vol 11, Iss 48, pp 9403-9419
Abstract: This paper presents a review of the phenomenon of interlayer exchange coupling in magnetic multilayers. The emphasis is put on a pedagogical presentation of the mechanism of the phenomenon, which has been successfully explained in terms of a spin-dependent quantum confinement effect. The theoretical predictions are discussed in connection with corresponding experimental investigations.
Record 6 of 27.
Title: Interlayer Exchange Coupling - Preasymptotic Corrections
Authors: Bruno-P
Full source: EUROPEAN PHYSICAL JOURNAL B 1999, Vol 11, Iss 1, pp 83-89
Abstract: In the asymptotic limit, the interlayer exchange coupling decays as D-2, where D is the spacer thickness. A systematic procedure for calculating the preasymptotic corrections, i.e., the terms of order D-n with n greater than or equal to 3, is presented. The temperature dependence of the preasymptotic corrections is calculated. The results are used to discuss the preasymptotic corrections for the Co/Cu/Co(001) system.
Record 7 of 27.
Title: On the Orientational Dependence of Giant Magnetoresistance
Authors: Blaas-C Weinberger-P Szunyogh-L Kudrnovsky-J Drchal-V Levy-PM Sommers-C
Full source: EUROPEAN PHYSICAL JOURNAL B 1999, Vol 9, Iss 2, pp 245-250
Abstract: The functional dependence of the giant magnetoresistance (GMR) with respect to the relative angle between the orientations of the magnetization in the magnetic labs of a trilayer system is calculated by using the Kubo-Greenwood formula for electrical transport together with the fully-relativistic spin-polarized screened Korringa-Kohn-Rostoker method for semi-infinite systems and the coherent potential approximation. It is found that the functional dependence of the GMR is essentially of the form (1 - cos phi).
Record 8 of 27.
Title: Helical Spin-Density Waves in Fe/Cr Trilayers with Perfect Interfaces
Authors: Fishman-RS
Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 5877-5879
Abstract: Despite the presence of only collinear, commensurate (C) and incommensurate (I) spin-density waves (SDWs) in bulk Cr, the interfacial steps in Fe/Cr multilayers are now believed to stabilize a helical (H) SDW within the Cr spacer. Yet HSDWs were first predicted in an Fe/Cr trilayer with perfect interfaces when the orientation of the Fe moments does not favor C ordering: if the number of Cr monolayers is even (odd) and the Fe moments are pointing in the same (opposite) direction, then a CSDW does not gain any coupling energy. Under these circumstances, a simple model verifies that H ordering is indeed favored over I ordering provided that the Fermi surface mismatch is sufficiently small or the temperature sufficiently high. (C) 1999 American Institute of Physics. [S0021-8979(99)67508-9].
Record 9 of 27.
Title: Exchange Coupling Between 2 Magnetic-Films Separated by an Antiferromagnetic Spacer
Authors: Rubinstein-M
Full source: JOURNAL OF APPLIED PHYSICS 1999, Vol 85, Iss 8, pp 5880-5882
Abstract: An expression for the interaction strength between two magnetic films separated by an insulating antiferromagnet spacer has been derived as a function of temperature and thickness. We consider the mechanism wherein the magnetic interaction between the ferromagnetic layers is mediated by the intervening antiferromagnetic insulator via the Suhl-Nakamura (SN) interaction. The interaction energy per unit area, sigma(SN), is derived as sigma(SN) = 1/8(J(C)(2)/J(AF))(delta/a)exp(-t/delta). Here, J(AF) is the magnetic coupling constant between nearest-neighbor antiferromagnetic spins in the spacer, J(C) is the effective coupling constant (which is greatly reduced from the Heisenberg exchange constant), between the spins in the ferromagnetic film and the nearest-neighbor spins in the antiferromagnetic spacer, t is the separation of the two ferromagnetic plates, and delta is the width of an antiferromagnetic domain wall. This mechanism is the antiferromagnetic analog of the Ruderman-Kittel oscillatory coupling between two magnetic films separated by a normal metal. [S0021-8979(99)67608-3].
Record 10 of 27.
Title: Morphology of Crystallites and Magnetic-Structure of Noncollinear Fe/Cr Multilayers
Authors: Krinitsina-TP Kravtsov-EA Lauterpassiouk-VV Lauter-HJ Popov-VV Romashev-LN Tsurin-VA Burkhanov-AM Ustinov-VV
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 203, Iss NSI, pp 181-183
Abstract: Atomic and magnetic structures of Fe/Cr superlattices have been studied by means of polarized neutron reflectometry, X-ray diffraction, electron microscopy and Mossbauer spectroscopy. Peculiarities of structure responsible for the formation of non-collinear magnetic order have been found. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 11 of 27.
Title: Effect of Roughness, Frustration, and Antiferromagnetic Order on Magnetic Coupling of Fe/Cr Multilayers
Authors: Pierce-DT Unguris-J Celotta-RJ Stiles-MD
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 290-321
Abstract: The interplay between interfacial disorder and the antiferromagnetic order in Cr lends to complex behavior in Fe/Cr multilayers. Measurements of interlayer coupling are discussed for samples with different amounts of disorder ranging from optimally fabricated trilayers of Fe/Tr/Fe on Fe(0 0 1) whiskers, to trilayers with increasing degrees of interfacial roughness, and finally to superlattices of Fe/Cr. The coupling of ferromagnets through noble-metal spacer layers can be described by a model that consists of bilinear coupling averaged over thickness fluctuations and extrinsic biquadratic coupling induced by the thickness fluctuations. This, the conventional model, also describes much of the behavior observed for Fe/Cr multilayers. However, in this case, the antiferromagnetism in Cr lends to results not explained by the conventional model. For nearly ideal interfaces, the Fe-Cr coupling can induce order in Cr, modifying the temperature dependence of the interlayer coupling. In addition, interfacial disorder can frustrate the antiferromagnetic order in the Cr, leading to a variety of ordered states which have been observed by neutron scattering. Each of these ordered states, in turn modifies the interlayer coupling in unexpected ways. The different ways in which the systems minimize the frustration can explain the experimental results. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 12 of 27.
Title: Hard/Soft Magnetic Heterostructures - Model Exchange-Spring Magnets
Authors: Fullerton-EE Jiang-JS Bader-SD
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 392-404
Abstract: An overview is provided of research on exchange-spring coupled magnetic films and multilayers, including fabrication methods, and the characterization and modeling of the magnetization reversal processes. For coupled hard/soft bilayers and multilayers the deposition process provides nanometer-scale control of thicknesses and magnetic anisotropy. Such magnetic heterostructures provide model systems for studying the exchange hardening mechanism. Recent work on epitaxial SmCo/Fe and SmCo/Co bilayers and superlattices that display many of the characteristic features of exchange-spring magnets is highlighted. Comparison of the experimental results with numerical simulations indicates that the exchange-spring behavior can be understood from the intrinsic parameters of the hard and soft layers. The simulations are extended to realistically estimate the ultimate gain in performance that can potentially be realized in permanent magnets based on the exchange-spring principle. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Record 13 of 27.
Title: Noncollinear Magnetic States in Fexco1-X/Mn-N Multilayers
Authors: Cornea-CC Stoeffler-DCA
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 282-284
Abstract: We study the non-collinear magnetism of FexCo1-x/Mn-n multilayers which are particularly interesting for their experimental behaviour as well as for theoretical reasons because they allow to study the magnetic properties of thin Mn layers with varying boundary conditions by changing the concentration x. For perfect interfaces, even if a non-collinear Mn spacer is obtained for small Fe concentrations when collinear solutions are expected, the interlayer coupling energy follows a parabolic law as a function of the angle between successive ferromagnetic magnetizations. We also examine the role of interfacial monoatomic steps on the magnetic order in such multilayers. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 14 of 27.
Title: The Role of Interface Alloying on Interlayer Exchange Coupling and the Magnetic State of Mn(001) in Fe Whisker/Cr/Mn/Fe(001) Structures
Authors: Monchesky-T Heinrich-B Cochran-JF Klaua-M
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 199, Iss JUN, pp 421-424
Abstract: Fe whisker/Cr/Fe(001) samples can be prepared in a nearly perfect layer by layer growth. It will be shown that the initial reversal of the phase in the short wavelength oscillations of the interlayer exchange coupling is most likely caused by the presence of interface alloying at the Fe/Cr interface. The ability to grow nearly perfect layers of Mn between Cr and Fe layers allows one to investigate the role of a strong intrinsic antiferromagnet, Mn, on the exchange coupling through the weak antiferromagnetic spin density wave in Cr. It will be shown that the Mn layers do not affect the sign of the interlayer exchange coupling. The sign of the exchange coupling is given by the number (parity) of pure Cr atomic layers. These results are consistent with recent theoretical calculations that predict the BCT Mn on Fe is antiferromagnetic with fully compensated (001) atomic planes. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 15 of 27.
Title: Noncollinear Magnetism of Fe Cr Films and Multilayers
Authors: Uzdin-VM Yartseva-NS Yartsev-SV
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 197, Iss MAY, pp 70-72
Abstract: The noncollinear magnetic structure of Fe overlayers on the stepped Cr substrate is calculated within the framework of a model Hamiltonian approach. Different noncollinear solutions are found by choosing the initial state for the self-consistency procedure. It is shown that for the stepped Fe/Cr interface the ground slate is noncollinear and the distribution of magnetic moment directions is not uniform in both the Fe and Cr layers. The dependence of the angle between the average moment of the Fe overlayer and the average moment of different Cr layers on the thickness of Fe coverage is obtained. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 16 of 27.
Title: Magnetic Multilayers - Interlayer Coupling in Fe/Cr/Fe
Authors: Rezende-SM Chesman-C Lucena-MA Demoura-MC Azevedo-A Deaguiar-FM
Full source: MATERIALS SCIENCE FORUM 1999, Vol 302-, pp 64-75
Abstract: The exchange coupling between neighboring magnetic lavers in multilayer systems consisting of stacks of ferromagnetic layers separated by nonmagnetic metallic layers plays a central role in the properties of these novel artificially structured materials. Here we review the most common techniques for measuring this coupling, namely magneto-optical Kerr effect magnetometry, Brillouin light scattering and ferromagnetic resonance. The theoretical background for interpreting experimental data in trilayers formed by two magnetic layers separated by a nonmagnetic layer is presented, based on a phenomenological model energy including bilinear and biquadratic exchange couplings, as well as surface, in-plane uniaxial and crystalline cubic anisotropy contributions. Accurate quantitative values for the coupling constants and the other magnetic parameters are measured in the prototype system (100) Fe/Cr/Fe grown by sputtering for several Cr spacer thickness. Consistent values are obtained with all three techniques for both the bilinear (J(1)) and biquadratic (J(2)) exchange coupling constants. In most of the Cr thickness range corresponding to the first antiferromagnetic peak, J(2) follows J(1) with a ratio J(2)/\J(1)\ congruent to 0.1. In the range corresponding to the second antiferromagnetic peak J(2) also follows J(1), but with a much larger ratio J(2)/\J(1)\ congruent to 1.0, indicating that the origin of the biquadratic coupling in the two ranges resides in different mechanisms.
Record 17 of 27.
Title: Correlation of Short-Period Oscillatory Exchange Coupling to Nanometer-Scale Lateral Interface Structure in Fe/Cr/Fe(001)
Authors: Schmidt-CM Burgler-DE Schaller-DM Meisinger-F Guntherodt-HJ
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 6, pp 4158-4169
Abstract: We investigate Fe/Cr/Fe(001) trilayers grown on AE(001)/Fe/GaAs(001) substrates at different temperatures. By changing the substrate temperature of the bottom Fe film during deposition, but otherwise keeping the preparation parameters constant, we are able to tailor the roughness of the Fe/Cr interfaces. The interfaces are characterized by means of scanning tunneling microscopy (STM). In these differently prepared systems, a clear change of the short-period oscillation amplitude is observed by magneto-optical Kerr effect measurements. A statistical analysis of the STM images allows us to extract the lateral length scale over which the Cr thickness is constant, and it turns out that areas of constant Cr thickness with a diameter larger than 3-4 nm are mandatory for the evolution of short-period oscillations. Two mechanisms are discussed which can explain the observed correlation between structure and magnetism, one linked to the propagation of the coupling through the spacer and the other to the response of the ferromagnetic layers to the transmitted exchange field. [S0163-1829(99)04430-6].
Record 18 of 27.
Title: Exchange Coupling Through Spin-Density Waves in Cr(001) Structures - Fe-Whisker/Cr/Fe(001) Studies
Authors: Heinrich-B Cochran-JF Monchesky-T Urban-R
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 22, pp 14520-14532
Abstract: Exchange coupling through a spin-density wave in Fe-whisker/Cr/Fe(001) structures has been studied using Brillouin light scattering (BLS) and magneto-optical Kerr effect (MOKE). The Fe-whisker(001) substrates provide nearly ideal templates: they are characterized by atomic terraces having dimensions in excess of several micrometers. Such templates are essential for the study of short-wavelength exchange coupling which is mediated by the intrinsic spin-density wave in Cr(001). Atomically smooth Cr(001) layers similar to those of the Fe-whisker surfaces can be grown at raised substrate temperatures. Angular resolved auger electron spectroscopy measurements have shown that the Fe-whisker/Cr(001) interfaces are affected by an atom exchange placement mechanism (interface alloying). It will be shown that this interface alloying at the Fe-whisker/Cr interface profoundly affects the behavior of the short-wavelength oscillations. The phase of the short-wavelength oscillations is reversed compared to that expected for the spin-density wave in Cr(001), The strength of coupling is significantly decreased from that obtained from first-principles calculations, and the first crossover to antiferromagnetic coupling occurs at 4 ML. BLS and MOKE have shown unambiguously that the exchange coupling in Fe-whisker/Cr/Fe(001) structures can be described by bilinear and biquadratic terms. Experiments carried out using Cu and Ag atomic layers between the Cr(001) and Fe(001) films, i.e., heterogeneous interfaces, have shown that the exchange coupling in Cr(001) is strongly affected by electron multiple scattering. It will be argued that the exchange coupling through thick (>8 ML) and atomically smooth Cr(001) spacers can be described by localized interactions (Heisenherg type) and by electron multiple-scattering (quantum well state) contributions. This is in good accord with recent first-principle calculations by Mirbt and Johansson. However, interface alloying severely affects the behavior of the exchange coupling for Cr thicknesses less than 8 ML. In this thickness regime the overall coupling exhibits mostly a long-wavelength behavior with a small superimposed short-wavelength contribution. This initial Cr thickness regime is responsible for changes in the phase of the short-wavelength oscillations and for the reduced strength of the exchange coupling due both to the localized and to the multiple-scattering contributions. We have observed no significant dependence of the exchange-coupling strength on the Fe film thickness for samples having the structure Fe-whisker/11Cr/nFe/20Au where n specifies an iron film thickness between 5 and 40 ML. However, preliminary data show that the exchange coupling is significantly increased in specimens for which both sides of the iron film are covered by Cr, i.e., for structures of the form Fe-whisker/11Cr/nFe/11Cr/20Au. It appears that electron resonant states in the iron film play no important role in the strength of the exchange coupling when the iron is bounded on one side by the gold, but that they do become important when the iron film is bounded by Cr on both sides. BLS and MOKE studies on Fe-whisker/Cr/Mn/Fe/(001) samples revealed that the antiferromagnetic state of Mn is composed of compensated (001) atomic plants. The results of the above experimental studies will be compared to recent theories. Points of agreement and of disagreement between the experimental results and recent first-principles calculations will be explicitly pointed out. [S0163-1829(99)10921-4].
Record 19 of 27.
Title: Oscillatory Interlayer Coupling in Fe/Mn/Fe Trilayers
Authors: Yan-SS Schreiber-R Voges-F Osthover-C Grunberg-P
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 18, pp 11641-11644
Abstract: Fe/Mn/Fe wedged-shape sandwiches were prepared by molecular beam epitaxy under optimal conditions. The interlayer coupling measured by magneto-optic Kerr effect is very strong for thin Mn layers. The canted angle between the magnetization vectors of the two magnetic layers in remanence increases gradually from 0 degrees to about 180 degrees and then gradually reduces to 90 degrees for Mn thicknesses from 0.62 to 1.2 nm. For Mn layer thicknesses in the range between 1.2 and 2.45 nm, the interlayer coupling is always 90 degrees coupling, but its strength oscillates with a short period of about 2 Mn monolayers. The above coupling phenomenon can be well described by the proximity magnetism model. [S0163-1829(99)50618-8].
Record 20 of 27.
Title: Spin-Density-Wave in Fe/Cr Superlattices - A First-Principles Study
Authors: Hirai-K
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 10, pp R6612-R6615
Abstract: A first-principles electronic-structure calculation for Fe/Cr superlattices is presented, where a spin-density-wave order in the Cr layer is considered in addition to an antiferromagnetic one. The interlayer magnetic coupling between ferromagnetic Fe layers is investigated, and the oscillation of the interlayer magnetic coupling with a two-monolayer period of the spacer thickness of the Cr layer is illustrated. The appearance of the spin-density-wave order in the Cr layer, which gives rise to a phase slip of the oscillation. is furthermore demonstrated. [S0163-1829(99)51010-2].
Record 21 of 27.
Title: Evidence for Roughness Driven 90-Degrees Coupling in Fe3O4/NiO/Fe3O4 Trilayers
Authors: Vanderheijden-PAA Swuste-CHW Dejonge-WJM Gaines-JM Vaneemeren-JTWM Schep-KM
Full source: PHYSICAL REVIEW LETTERS 1999, Vol 82, Iss 5, pp 1020-1023
Abstract: The magnetic interlayer coupling of Fe3O4 across NiO is studied using Fe3O4/NiO/Fe3O4 trilayers epitaxially grown on (001) MgO substrates. For NiO thicknesses between 0.7 and 5 nm, the magnetic moments of the two Fe3O4 layers are directed perpendicularly with respect to each other. The 90 degrees coupling strength is determined to be 0.35 +/- 0.08 mJ/m(2) for a 1.4-nm-thick NiO spacer. The 90 degrees coupling can be understood from the effect of an antiferromagnetic spacer in the presence of interface roughness.
Record 22 of 27.
Title: Phase-Diagram of Multilayer Ferromagnet-Layered-Antiferromagnet Structures
Authors: Morozov-AI Sigov-AS
Full source: PHYSICS OF THE SOLID STATE 1999, Vol 41, Iss 7, pp 1130-1137
Abstract: This paper discusses the thickness-roughness phase diagram of a three-layer system consisting of two ferromagnetic layers separated by an antiferromagnetic interlayer. It is shown that the stability region of single-domain ferromagnetic layers is determined by the ratio between the width of the atomic steps that appear at the interfaces of the layers during their growth and the thicknesses of the layers, and also by the values of the interlayer and intralayer exchange interactions. A basis is provided for the phenomenological ''magnetic closeness'' model proposed by Slonczewski, and an expression is obtained for the constants of this model. (C) 1999 American Institute of Physics. [S1063-7834(99)02407-7].
Record 23 of 27.
Title: Field-Induced Spin-Reorientation Transitions in Magnetic Superlattices with Uniaxial Anisotropy and Biquadratic Exchange
Authors: Zvezdin-AK Kostyuchenko-VV
Full source: PHYSICS OF THE SOLID STATE 1999, Vol 41, Iss 3, pp 413-415
Abstract: Phase transitions induced by an external field are investigated in magnetic multilayer systems with uniaxial anisotropy and biquadratic exchange. A magnetic field directed perpendicular to the plane of the layers changes the effective anisotropy and exchange constants, determining the orientation of the magnetization in the plane of the layers, and can give rise to spin-reorientation transitions. All possible types of such transitions are investigated for the case of uniaxial anisotropy, which differs substantially from the case of cubic anisotropy by the different renormalization of the effective anisotropy constants. (C) 1999 American Institute of Physics. [S1063-7834(99)01803-1].
Record 24 of 27.
Title: Investigation of Magnetic Coupling Phenomena in Fe1-Xcrx/Cr-Superlattices with Spin-Polarized Neutrons
Authors: Siebrecht-R Schreyer-A Schmitte-T Schmidt-W Zabel-H
Full source: PHYSICA B 1999, Vol 268, Iss JUN, pp 207-210
Abstract: We present the results of temperature dependent measurements of magnetically coupled Fe1-xCrx/Cr-superlattices. These results are supplementary to the ones known for non-collinearly coupled Fe/Cr-superlattices. By systematically varying the Cr concentration x we cover a wide range of the Fe1-xCrx-phase diagram. As an experimental technique spin-polarized neutron reflectivity with spin analysis and high-angle neutron scattering proves to be ideal for this work. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Record 25 of 27.
Title: Mossbauer-Spectroscopy of Interlayer Boundaries in Magneto-Noncollinear (Fe-57/Cr)(12)/MgO(100) Superlattices
Authors: Ustinov-VV Tsurin-VA Romashev-LN Ovchinnikov-VV
Full source: TECHNICAL PHYSICS LETTERS 1999, Vol 25, Iss 6, pp 459-461
Abstract: Results are presented of Mossbauer analyses of [Fe-57/Cr](12)/MgO (100) superlattices. A combined approach was used, based on model calculations and a method of reconstructing the density distribution function P(H-hf) of the hyperfine fields. This procedure allowed us to systematically subtract the subspectra from the different neighborhood configurations of the resonant Fe-57 atom. A detailed structural model was obtained for the Fe-Cr transition region from a ''pure'' Fe layer to a ''pure'' Cr layer. A deflection of the magnetic moment of the Fe atoms from the plane of the superlattice layers was identified in the interface of the Fe and Cr layers. The specific magnetic structure of the interface regions with different angular orientations of the magnetic moments of the Fe atoms relative to the plane of the layers (between 0 and 90 degrees) is attributed to the coexistence of strong antiferromagnetic interaction between Fe and Cr atoms and an incommensurate spin density wave in the Cr layers. (C) 1999 American Institute of Physics. [S1063-7850(99)01606-7].
Record 26 of 27.
Title: Interlayer Exchange Coupling
Authors: Stiles-MD
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 322-337
Abstract: The extensive research done on interlayer exchange coupling in transition metal multilayers has resulted in a deep understanding of this coupling and a remarkable agreement between theoretical results and measurements. The coupling between two magnetic layers separated by a non-magnetic spacer layer is mediated by the electrons of the spacer layer. The coupling, which oscillates in sign as a function of the thickness of the spacer layer, is closely related to the well-known RKKY interaction between magnetic impurities. Due to the existence of many high-quality measurements, it has been much more fully developed theoretically than the interaction between impurities. Theory predicts that the periods of the oscillatory coupling should depend on critical spanning vectors of the Fermi surface belonging to the spacer-layer material There is remarkable agreement far the measured periods and those predicted from the Fermi surfaces. There is also substantial agreement between theory and experiment on the strength of the coupling. This review presents the comparison between theory and experiment in some detail. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Record 27 of 27.
Title: New-Type of Domain-Walls in Multilayer Magnetic-Structures
Authors: Morozov-AI Sigov-AS
Full source: USPEKHI FIZICHESKIKH NAUK 1999, Vol 169, Iss 8, pp 922-924
SCI CDE with Abstract:s (Jan 99 - Dec 99) (D4.1)
Field:: Cited author/reference
Statement:: KOHLHEPP-J-1997-PHYS-REV-B-V55-PR696
Record 1 of 6.
Title: Magnetic-Properties and Magnetoresistance of Granular Evaporated Fe/Si Films
Authors: Ihara-N Narushima-S Kijima-T Abeta-H Saito-T Shinagawa-K Tsushima-T
Full source: JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 1999, Vol 38, Iss 11, pp 6272-6281
Abstract: Fe (3.4 Angstrom) and Si (6 Angstrom) are evaporated alternately onto silica substrates to realize a granular structure. The substrate temperature T-s during the evaporation is changed from 100 K to 623 K to vary the film structures. The specimens of T-s greater than or equal to room temperature (RT) are superparamagnetic at RT, which suggests a granular structure. Magnetoresistance (MR) at RT is negative (resistivity decreases with increasing magnetic field H) for all specimens. It is thought that the negative MR is attributable to the granular structure. On the other hand, at 77 K a positive MR linear with H (not H-2) up to 50 kOe is observed for all specimens. The linear dependence on H of the positive MR may be due to the nonuniformity in the granular structure. The positive MR itself and the change of the sign of MR from negative to positive with decreasing temperature have not been observed in conventional granular systems such as Co-Ag and Co-Al-O.
Record 2 of 6.
Title: Polarized-Neutron Reflectometry
Authors: Ankner-JF Felcher-GP
Full source: JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 1999, Vol 200, Iss 1-3, pp 741-754
Abstract: Polarized-neutron specular reflectometry (PNR) was developed in the 1980s as a means of measuring depth-resolved magnetization in flat films with characteristic thicknesses from 2 to 5000 Angstrom. PNR has been widely used to study homogeneous and heterogeneous magnetic films, as well as superconductors. Starting from simple profiles, and gradually solving structures of greater complexity, PNR has been used to observe or clarify phenomena as diverse as the magnetism of very thin films, the penetration of fluxoids in superconductors, and the magnetic coupling across non-magnetic spacers. Although PNR is considered to be a probe of depth-dependent magnetic structure, laterally averaged in the plane of the him, the development of new scattering techniques promises to enable the characterization of lateral magnetic structures. Retaining the depth-sensitivity of specular reflectivity, off-specular reflectivity can resolve in-plane structures over nanometer to micron length scales. Presently limited by the neutron fluxes available, neutron reflectivity is expected to blossom in the next century, thanks to the increased brightness of the neutron beams, due not only to continuing improvements in neutron optics, but especially to the advent of second-generation spallation neutron sources. (C) 1999 Elsevier Science B.V. All rights reserved.
Record 3 of 6.
Title: Pinholes in Antiferromagnetically Coupled Multilayers - Effects on Hysteresis Loops and Relation to Biquadratic Exchange
Authors: Bobo-JF Kikuchi-H Redon-O Snoeck-E Piecuch-M White-RL
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 60, Iss 6, pp 4131-4141
Abstract: We present a micromagnetic study of the influence of ferromagnetic bridges between consecutive ferromagnetic layers in antiferromagnetically coupled multilayers. The model is compared with experimental results for hysteresis loops obtained from the multilayer systems Co-Cu and FeNi-Ag. The presence of pinholes in Cu-Co multilayers is confirmed by transmission electron microscopy. We demonstrate that low densities of ferromagnetic pinholes in such multilayers are sufficient to give rise to significant deviations from the expected bilinear interlayer coupling and modify the observed interlayer: oscillatory exchange coupling. The effects of pinholes can be simulated in certain cases by biquadratic exchange coupling, and we propose a magnetic phase diagram which correlates the apparent bilinear and biquadratic couplings to the pinholes density, size, and interlayer exchange strength. [S0163-1829(99)14529-6].
Record 4 of 6.
Title: Cohesive, Structural, and Electronic-Properties of Fe-Si Compounds
Authors: Moroni-EG Wolf-W Hafner-J Podloucky-R
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 20, pp 12860-12871
Abstract: Phase stability, structural, and electronic properties of iron silicides in the Fe3Si, FeSi, and FeSi2 compositions are investigated by first-principle density-functional calculations based on ultrasoft pseudopotentials and all-electron methods. Structural stabilization versus spin-polarization effects are discussed at the Fe3Si composition, while for epsilon-FeSi and beta-FeSi2 we investigate their structural properties and the corresponding semiconducting band properties. All the computed results are analyzed and compared to available experimental data. The stability of the bulk phases, the lattice parameters, the cohesive energies and magnetic properties are found to be in good agreement with experiment when using the generalized gradient approximations for the exchange-correlation functional. Density-functional calculations are unable to account for the small bulk modulus of epsilon-FeSi despite that the computed lattice constant and internal atomic positions coincide with the experimental results. Both full-potential and ultrasoft-pseudopotential methods confirm for beta-FeSi2 the indirect nature of the fundamental gap, which is attributed to a transition between Y to 0.6X Lambda being 30% smaller than the experimental gap. Ultrasoft pseudopotential calculations of Fe-Si magnetic phases and of various nonequilibrium metallic phases at the FeSi and FeSi2 composition are presented. These calculations provide nb initio information concerning the stabilization of metallic pseudomorphic phases via high pressures or epitaxy. [S0163-1829(99)05419-3].
Record 5 of 6.
Title: Interlayer Coupling in Fe/Fe1-Xsix Superlattices
Authors: Endo-Y Kitakami-O Shimada-Y
Full source: PHYSICAL REVIEW B-CONDENSED MATTER 1999, Vol 59, Iss 6, pp 4279-4286
Abstract: Interlayer coupling has been investigated for a series of Fe/Fe1-xSix (0.4 less than or equal to x less than or equal to 1.0) superlattices. The layer of Fe1-xSix in the lattices is ferromagnetic for x<0.5 and causes ferromagnetic coupling between Fe layers for all spacer thicknesses investigated here. As the Si content increases above x=0.5, the layer becomes nonmagnetic and simultaneously our current in the plane of the sample and current perpendicular to the sample plane measurements suggest that the spacer rapidly changes its conduction property from metallic to highly resistive. Variations of the interlayer magnetic coupling as a function of spacer layer thickness for the spacer compositions above x=0.5 are similar to each other; namely, with an increase of the spacer thickness the interlayer coupling is initially ferromagnetic, then antiferromagnetic, and finally becomes noncoupling. Moreover, the temperature dependence of the bilinear and biquadratic coupling constants, J(1)(T) and J(2)(T) which were obtained by numerical fitting, varies sensitively with x. Assuming that the conduction of the spacers ranges from metallic to insulating as x increases, all these coupling behaviors can be described qualitatively by the quantum interference model formalized by Bruno. Furthermore, we found that the coupling strength is enhanced dramatically with increase of x of Fe1-xSix. [S0163-1829(99)11405-X].
Record 6 of 6.
Title: Polarized Neutron Reflectometry - A Historical-Perspective
Authors: Felcher-GP
Full source: PHYSICA B 1999, Vol 268, Iss JUN, pp 154-161
Abstract: Born in the early 1980s to study magnetic films, polarized neutron reflectometry (PNR) has enjoyed growing popularity as witnessed by the number of instruments assembled at neutron research centers. PNR has proved its usefulness by providing information as diverse as the penetration depth of the magnetic field in superconductors and the absolute value of the magnetic moments in ultrathin ferromagnetic layers; yet its widest application has become the study of the magnetic configurations in multilayers. Two types of reflectometers have been constructed: time of flight and crystal analyzer. The relative merits of the two types are discussed in the light of present and future applications, (C) 1999 Published by Elsevier Science B.V.
Márton Major